1. Field of the Invention
The present invention relates to an image forming apparatus such as a facsimile, a copying machine and the like, having an improved sheet convey path.
2. Related Background Art
As an example of a conventional image forming apparatus, a facsimile apparatus will be described with reference to FIG. 7. FIG. 7 shows a facsimile apparatus as an image forming apparatus in which a sheet conveying apparatus L is used in a sheet discharge portion (discharge portion) for discharging a sheet.
In FIG. 7, the facsimile apparatus comprises a main body or frame 101, a cartridge cover 102 also acting as an original stacking plate on which a plurality of originals S can be stacked, an image reading portion 103 for reading image information on the original S, a recording device (laser beam printer) 104, an original convey portion 105, an original urging portion 106, an image sensor 107 of contact type, an original discharge tray 108, a laser scanner 109, an image forming portion (image forming means) 110, a manual insertion sheet supply portion 111, a face-down recording sheet discharge tray 112 including a sheet discharge tray 156 of the sheet conveying apparatus L, a cassette portion 113, a recording sheet convey path switching flapper 114, a face-down guide 115, an upper original guide 116, a lower original guide 117, an operation portion 125, a display portion 126, a convey guide 127, a rear cover 128, and a convey roller 129.
In the image reading portion 103, first of all, the originals (sheets) S stacked on the original stacking plate 102 are separated and supplied one by one by a friction piece 118 and a separation roller 119 urged against the friction piece, and, then, the separated original is conveyed to the image sensor 107 of contact type by means of a sheet supply sub-roller 121 urged by an urging spring 120 and a sheet supply roller 122 urged against the sheet supply sub-roller 121, and, then, the original is urged against the image sensor 107 of contact type in the original urging portion 106, so that the image information on the original S is read by the image sensor 107 of contact type. Thereafter, the original S is discharged onto the original discharge tray 108 by means of a sheet discharge sub-roller 123 urged by the urging spring 120 and a sheet discharge roller 124 urged against the sheet discharge sub-roller 123. Meanwhile, the original S is guided by the upper and lower original guides 116, 117.
The original stacking plate 102 is provided with a slider 102a slidable in a direction (original width-wise direction) perpendicular to a conveying direction of the original S. Both lateral edges of the originals S stacked on the original stacking plate 102 can be aligned with each other by the slider 102a. When the original S is elongated, rear parts of the originals S can be prevented from protruding from and being suspended from the original stacking plate 102 by means of an original tray 102b.
In the recording device 104, a modulated signal (modulated beam) is emitted from a laser beam generating device 109a of the laser scanner 109 in response to an image signal outputted from a control portion, and the modulated beam is illuminated (as a scan beam) onto a photosensitive drum 110a of the image forming portion 110 through a polygon mirror 109b, thereby forming the image information on the photosensitive drum 110a. After the image information is transferred onto and fixed to a recording paper sheet (sheet) P supplied from the manual insertion sheet supply portion 111 or the cassette portion 113 to the image forming portion 110, the recording sheet P is discharged onto the recording sheet stacking tray 112.
The photosensitive drum 110a is integrally incorporated into a recording cartridge 110e (which is detachably mounted on the main body 101) together with a first charger 110b, a developing roller 110c and a cleaning blade (not shown). A surface of the photosensitive drum 110a is uniformly charged by the first charger 110b. When the scan beam sent from the polygon mirror 109b is illuminated onto the charged surface of the photosensitive drum through a reflection mirror 109c, a latent image is formed on the photosensitive drum. The latent image is visualized as a toner image by toner supplied from the developing roller 110c.
A transfer charger 110f is disposed around the photosensitive drum 110a of the image forming portion 110. Further, in a recording sheet convey path at a downstream side of the photosensitive drum 110a, there are disposed a thermal fixing device 110g, a pair of discharge rollers 110h, and a rubber roller 152 and a pinch roller 154 (constituting a pair of face-down sheet discharge rollers of the sheet conveying apparatus L).
After the toner image formed on the surface of the photosensitive drum 110a is transferred to the recording sheet P by the transfer charger 110f, the recording sheet is conveyed, along the convey guide 127, to the thermal fixing device 110g, where the toner image is fixed to the recording sheet. Thereafter, the recording sheet is sent to the pair of discharge rollers 110h. An operator can select one of two recording sheet output modes (so-called "face-down discharge mode" and "face-up discharge mode"). The face-down discharge mode means a mode in which the recording sheets are discharged with imaged surfaces thereof facing downwardly in a page order or sequence, and the face-up discharge mode means a mode in which the recording sheets are discharged with imaged surfaces thereof facing upwardly so that the outputted contents can be observed or ascertained during the discharging operation. The modes can be switched by switching the convey path by shifting the recording sheet convey path switching flapper 114.
FIG. 7 shows a condition that the apparatus is in the face-down discharge mode. In this condition, the recording sheet P directed upwardly by the flapper 114 is guided along the face-down guide 115 and then is discharged onto the face-down recording sheet discharge tray 112 by the rubber roller 152 and the pinch roller 154 (constituting the pair of face-down sheet discharge rollers).
When the operator selects the face-up discharge mode, the flapper 114 is switched by a switching lever (not shown) so that the original is discharged toward the original discharge tray 108. The original discharge tray 108 also acting as the face-up discharge tray is formed from metal wires so that the operator does almost not feel the fact that any obstacle exists at a front side of the apparatus even when the operator stands at the front side of the apparatus.
The cassette portion 113 is disposed at a bottom of the main body 101. A recording sheet stack P contained in a cassette container 131 is urged against separation roller 160 by rotating an intermediate plate 136 upwardly by means of a lifter arm (supplying force providing means) 138 so that the recording sheets P can be separated one by one by a separation pad 173 (friction piece separating system). The separated recording sheet is conveyed along a separation guide 175 and is reversely rotated by the convey roller 129, a cover side U-turn guide 128a provided on the rear cover 128 and a main body side U-turn guide 128b provided on the main body 101.
During the supplying operation, a tip end of the recording sheet P is detected by a regist sensor 128c. After a sheet supplying timing and an image outputting timing are adjusted so that a tip end of the toner image formed on the photosensitive drum 110a is aligned with the tip end of the recording sheet P, the recording sheet is conveyed to a nip between the transfer charger 110f and the photosensitive drum 110a. The image is recorded on a surface of the recording sheet which is a lower surface when the sheet is in the cassette portion 113.
Lateral edges and rear edges of the recording sheets P are regulated by a width regulating plate 133 and a rear end regulating plate 134 which can be shifted in accordance with the size of the recording sheet, thereby preventing skew-feed and poor conveyance of the recording sheet. The stackable number of recording sheets is about 250 (sheets) and the cassette portion can be retracted toward the front side of the apparatus (front loading type). Three kinds of sheet having A4 size, LTR size and Regal size can be used with this apparatus. Incidentally, in FIG. 7, the rear end regulating plate 134 is set at a position corresponding to the LTR size sheet.
The manual insertion sheet supply portion 111 is disposed on the rear cover 128. A recording sheet P inserted into the manual insertion sheet supply portion 111 is sent to the image forming portion 110 by the convey roller 129 and a sub-roller 128.sub.1 provided on the U-turn guide 128b. The main body 101 is provided with the open/close cartridge cover 102. When the cartridge cover 102 is opened, the recording cartridge 110e can be replaced by a new one.
In the illustrated facsimile apparatus, the cartridge cover 102 is provided with an interlock mechanism so that the recording device 104 cannot be operated if the cartridge cover 102 is opened or if the recording cartridge 110e is not mounted within the main body 101.
A drum exposure preventing shutter (not shown) of the recording cartridge 110e is operated in synchronous with the setting of the recording cartridge 110e with respect to the main body 101. That is to say, the shutter is opened when the cartridge cover 102 is opened and the recording cartridge 110e is mounted within the main body 101; whereas, the shutter is closed when the recording cartridge 110e is dismounted from the main body 101 so that unwanted exposure of the photosensitive drum 110a is prevented.
During the recording operation, if the sheet is jammed, the recording sheet P jammed with the main body 101 can be removed by opening the cartridge cover 102, rear cover 128, face-down guide 115 or cassette portion 113. In the image sensor 107 of contact type, light from an LED array (light source) is illuminated onto the imaged surface of the original S, and light reflected from the imaged surface is focussed on a sensor element through a SELFOC (trade mark) lens, thereby reading the image information.
As indicated above, in the conventional image forming apparatus, there has been proposed the reading system arranged at the front side (left side in FIG. 7) of the recording system.
However, in the above-mentioned conventional example, since the originals passed through the reading portion are stacked on the tray protruding from the apparatus, a space must be reserved at the front side of the apparatus. Further, if the discharged originals are left as they are, since it is difficult to access to the operation portion the operability will be worsened.
If the tray is removed, although the apparatus becomes compact, good arrangement of the discharged originals cannot be ensured, and, thus, the page sequence may be disordered. Further, regarding the apparatus shown in FIG. 7, in the face-up discharge mode, since both the originals and the recording sheets are stacked on the tray, the originals and the recording sheets may be mixed.